In a fusion reactor, materials will be subjected to significant fluxes of high-energy neutrons. As well as causing radiation damage, the neutrons also initiate nuclear reactions leading to changes in the chemical composition of materials (transmutation). Many of these reactions produce gases, particularly helium, which cause additional swelling and embrittlement of materials. This paper investigates, using both neutronics and inventory calculations, the variation in gas production levels (and transmutation rates) as a function of position within the high flux regions of a recent conceptual model for the ‘next-step’ fusion device DEMO. Additionally, simple modelling of grain structures and gas diffusion rates illustrates that the lifetime of components, limited by He embrittlement, varies widely between different materials.
